Hotshots is a rich features screenshots grabber on Linux. It has a simple GUI and has many features such as supports many image formats for output such as jpg, png, bmp and many others. Hotshots offers a default tool to upload scrennshots to online image storage services such as imgur, imageshack, freeimagehosting etc. There are 5 different capture modes available:

Grab screen

Grab all screen

Grab window

Grab region

Grab freehand region

Hotshots is a complete, easy to use screenshot capture. I prefer to use Hotshots other than the default screenshot application of Elementary OS Luna.